The present invention relates generally to a storage tank for a hot water system that includes a mechanical insulator for the separation of the hot layer and the cold layer.
Hot water systems commonly include a storage tank that stores the fluid, such as water, that cools the refrigerant in the heat rejecting heat exchanger. By employing a storage tank, the size, cost, and cycling of the hot water generation component can be reduced. In a heat pump system, hot water is generated outside of the storage tank. Heat pump system efficiency is directly related to the inlet temperature of the water in the heat sink which exchanges heat with the refrigerant. As the inlet temperature of the fluid into the heat sink decreases, system efficiency increases.
By flowing water into the storage tank slowly, a hot layer and cold layer can be formed in the storage tank which is separated by a thermal interface layer. The amount of hot water in the storage tank varies at any given time as the hot water generation capacity typically does not match the load demands of the system. Therefore, the thermal interface layer moves up and down in the storage tank as loads are placed on the system, and includes a range of temperatures between the hot layer and the cold layer.
There is also a concern about the formation of legionella in hot water storage tanks which occur between 25 to 42° C. and because of sediment and scaling.